1. Field of the Invention
This invention relates to a magnetic tape cartridge, and more particularly to a magnetic tape cartridge comprising a cartridge casing and a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation.
2. Description of the Related Art
There has been known a single reel magnetic tape cartridge, comprising a cartridge casing and a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation, as a recording medium for an external storage for a computer and the like. Such a single reel magnetic tape cartridge is used for retaining important data of a computer or the like and accordingly is arranged so that trouble such as tape jamming does not occur and the magnetic tape is not accidentally drawn out.
The reel is provided with a cylindrical reel hub having a closed bottom and stopper gear teeth are formed in a circle and a brake member provided with a brake gear which is adapted to be brought into engagement with the stopper gear teeth is disposed to be movable in the direction of thickness of the cartridge casing along the axis of rotation of the reel. The brake member is urged, for instance, by a coiled spring toward a position where the stopper gear teeth are engaged with the break gear to prevent rotation of the reel when the magnetic tape cartridge is not used. When the magnetic tape cartridge is loaded in a recording and reproducing system, a brake release spindle of the recording and reproducing system pushes upward the brake member to disengage the stopper gear teeth from the brake gear.
However if a space is formed between the brake member and the reel hub when the brake member is moved upward, dust and dirt can enter the inside of the cartridge casing through the space.
In view of the foregoing observations and description, the primary object of the present invention is to provide a magnetic tape cartridge in which dust and dirt can be prevented from entering the inside of the cartridge casing when the brake member is moved upward to permit rotation of the reel.
In accordance with the present invention, there is provided a magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation, the reel having a reel hub in the form of a cylindrical member which has a bottom wall and is provided with an opening and a stopper gear formed on the bottom wall, and a brake member which is provided with a brake gear and is movable up and down between an operative position where the brake gear is brought into engagement with the stopper gear to prevent rotation of the reel and a retracted position where the brake gear is disengaged from the stopper gear to permit rotation of the reel, the brake member being normally urged toward the operative position and moved to the retracted position by a pusher member of a tape drive system which acts on the brake member through the opening in the reel hub when the magnetic tape cartridge is loaded in the tape drive system,
wherein the improvement comprises that
a continuous wall portion is erected around the opening in the reel hub, and
the brake member comprises a horizontal portion which is disposed above the opening in the reel hub and receives force from the pusher member when the brake member is moved to the retracted position and a continuous skirt portion which extends downward from the horizontal portion and is in contact with the continuous wall portion of the reel hub, thereby closing the opening together with the horizontal portion, the brake member being moved between the operative position and the retracted position with the skirt portion kept in contact with the continuous wall portion of the reel hub.
It is preferred that the brake member comprises a first member and a second member which abuts against the first member from above and is movable up and down together with the first member, said horizontal portion and the skirt portion are formed on the first member and the brake member is urged toward the operative position by a spring means which acts on the second member.
The skirt portion may be fitted either on or in the continuous wall portion.
In the case where the brake member comprises the first and second members, it is preferred that the first and second members abut against each other by way of a projection and the first and/or second members be formed of low friction hard wearing material.
In the magnetic tape cartridge of the present invention, the skirt portion is kept in contact with the continuous wall portion on the reel hub to keep the opening closed even when the brake member is in the retracted position, entrance of dust and dirt into the cartridge casing through the opening can be prevented.